PDA

View Full Version : black hole upper limit?



Timebender13
2008-Sep-27, 11:20 PM
recently, there have been some news stories about the upper mass limit of black holes. How is this possable?!? They are, by definition, infinate. It just doesn't seem logical. Any explinations?

WayneFrancis
2008-Oct-01, 10:00 AM
recently, there have been some news stories about the upper mass limit of black holes. How is this possable?!? They are, by definition, infinate. It just doesn't seem logical. Any explinations?

Can you provide a reference to any of these?

The upper limit is probably a oberservational upper limit for galaxies central black hole. If they where actually bigger the galaxy would not survive.

RegisteredUsername
2008-Oct-01, 04:04 PM
One possible explanation put forth by Natarajan is that the black holes eventually reach the point when they radiate so much energy as they consume their surroundings that they end up interfering with the very gas supply that feeds them, which may interrupt nearby star formation. The new findings have implications for the future study of galaxy formation, since many of the largest galaxies in the universe appear to co-evolve along with the black holes at their centers.

I found it here (http://opa.yale.edu/news/article.aspx?id=5984).

Her paper is here (http://arxiv.org/abs/0808.2813).

Timebender13
2008-Oct-03, 03:35 AM
I suppose her arguement sounds plausable enough. The media, as usual, has twisted the meaning to make it sound contravercial.

As plausable as her hypothosis may be, however, is a black hole able to produce that much hawking radiation at once, no matter how big it may be?

slang
2008-Oct-03, 08:21 AM
I suppose her arguement sounds plausable enough. The media, as usual, has twisted the meaning to make it sound contravercial.

As plausable as her hypothosis may be, however, is a black hole able to produce that much hawking radiation at once, no matter how big it may be?

I don't think Hawking radiation has anything to do with this effect, but rather the interaction of SMBH jets (and other effects?) with gas in the host galaxy.

Timebender13
2008-Oct-06, 05:17 PM
I don't think Hawking radiation has anything to do with this effect, but rather the interaction of SMBH jets (and other effects?) with gas in the host galaxy.

What about a free-flying supermassive black hole, one not bound inside a galaxy? It could have been thrown free in a three body reaction and would have no interfearence from a galaxy.

slang
2008-Oct-06, 10:43 PM
What about a free-flying supermassive black hole, one not bound inside a galaxy? It could have been thrown free in a three body reaction and would have no interfearence from a galaxy.

What would it eat to grow? MRE's? :)

Timebender13
2008-Oct-07, 03:28 AM
Lol Just because it's not growing doesn't mean it can't grow.

slang
2008-Oct-07, 07:04 AM
Lol Just because it's not growing doesn't mean it can't grow.

Well, if you are asking if there is an absolute theoretical limit to how large an SMBH can grow before something happens that makes it not an SMBH anymore, I don't know. The practical limit is set by the earlier mentioned things. The bottom line is, it can't grow if there's nothing to eat :)

Also I'm not sure if it's right to say that they are by definition infinite. The math says that they will become infinitely dense. But there's no guarantee that what actually happens is accurately described by the math, and I think that (new?) physics may one day describe what really happens down there.

I'm stretching my own understanding here, perhaps you can try asking in the Questions & Answers forum, some quite knowledgeable chaps read there.

Timebender13
2008-Oct-08, 05:11 PM
Practical limit is not a factor. There will always be a way for a black hole to grow that neather of us is mentioning, and that scientists may never know about.

Another thing: What of the Big Crunch? Before that happens, all that would exist would be black holes. It would take a while, but they would eventually swallow each other up, the only limiting factor being the amount of matter in the universe!

My brain hurts...:doh: